1) Field of the Invention
This invention relates in general to fluid flow control devices and specifically to fluid flow control where incoming volume fluctuates.
2) Prior Art
Reservoirs & impoundments typically strive to retain maximum fluid levels for either storage or gravitational potential energy. For dams and weirs with fixed crests and natural volume inflow from rivers, streams, etc. increased inflow may cause undesirable flooding upstream of the dam or weir. Many devices have been used to regulate outflow to compensate for inflow variations. One such device is known as the steel pin flashboard, consisting of vertical steel pins, set into sockets on the crest of a dam, supporting horizontal wood planks or other such waterproof material that increases the effective height of the dam. As fluid level increases the pressure against the steel pins also increases until they bend over, allowing greater outflow from the impoundment.
Other devices use hydraulic cylinders to raise and lower hinged panels attached to the crest. Another variation is to use air or water to fill bags attached to the crest and alter the outflow by either filling or exhausting said bags.
Steel pin flashboards, once bent get washed away or remain down until flood levels recede enough to allow manual replacement. Hydraulically operated and air or water filled devices all rely on some form of external power for operation and all utilize an internal pressurized fluid to raise or lower their height and thereby the fluid level. Should loss of this internally pressurized fluid occur, sudden and dangerously unexpected flooding downstream of the impoundment is a possible consequence.
U.S. Pat. No. 4,787,774 utilizes cantilever mounted leaf springs to support a flexible impermeable membrane. Increased fluid pressure causes said leaf springs to deflect, allowing increased fluid flow over the membrane. However, any damage to the membrane will cause an opening to occur at least as wide as the spacing between the leaf springs. When in the fully lowered position bulges are created in the membrane by the leaf springs. These bulges subject the membrane in those locations to increased damage from large water born debris such as logs, ice sheets, etc.. Furthermore, the exposure of the bending element to the environment results in degradation of the bending element over time. Finally, by initiating the bend at the base, the exposed free end of the device will be impacted by water born debris normal to its plane, with possible damage occurring to the membrane.
Whatever the merits of the previously described devices, none of them fully achieves the advantages of the current invention.
Accordingly, it is a principle object of the invention to provide a novel, simple and durable device that when installed in a fluid passageway will automatically assume a blocking or unblocking position in response to changes in fluid pressure. This reaction shall occur without pumps, blowers, electrically or mechanically driven devices, sensors, wiring, piping, external springs, etc.
It is another object of this invention to be extremely resistant to punctures, tears, acts of vandalism including gunshot and knife cuts, and the damage possible from large water born debris and ice sheets. Should damage be inflicted on the device, any portion not damaged will continue to operate in its normal mode. Due to its construction, any portion of the device which is whole along an axis perpendicular to its support will be able to operate normally and independently should it become separated from any other portion of the device.
It is another object of the invention to flex from the top down in response to increased fluid pressure, thereby assuring any floating debris will strike tangentially to the device.